Thermal relay



Aug. 18, 1936. B. W. JONES THERMAL RELAY Filed D60. 29, 1934 inve mtor:Benjam im V\/. Jones,

n ifm/1765,

Ld His Attorney Patented Aug. 1h87, v1936 THERMAL RELAY Benjamin W.Jones, Schenectady, N. Y., assigner to General Electric Company, acorporation of New York Application December 29, 1934, Serial No.759,719 22 Claims. (C1200-122) paratus to dangerous temperatures. Inapplying thermal overload protection to such apparatus, it is oftendesirable or necessary that the entire control including the Ythermalrelay, be immersed in a body of oil, as for'instance, when the appaplacewhich is subject to explosive or corrosive atmospheres, and consequentlyconsiderable need has arisen for a thermal overload relay which willoperate satisfactorily when immersed in a body of oil.

The operation of thermal overload relays is to a large extent dependentupon the thermal propertics of the medium surrounding the thermalworking parts of the relay, and serious operating difficulties areencountered, therefore, in the design of thermal relays for oil immersedoperation. For example, the required Watt input to operate a thermalrelay in air is increased by approximately 400% when the relay isimmersed in a large body of oil.

This large watt input is of course unsatisfactory, and may be offset bythermally isolating the working parts of the relay from the large bcdyof oil. Resort may be had, for this purpose,

to the practice of enclosing the thermal working parts of the relay inan oil-lled sealed container of thermal insulating material, so that therelay parts are thermally associated with only a small body of oil whichis thermally isolated from the main body of immersing oil.

Operating diiculties are again encountered, however, due to thesusceptibility of the sealed container to leakage. relay requires thatthe thermal parts of theyrelay be subjected at all times to the sameambient medium, and it will be apparent that if the sealed containerdevelops a leak before the relay is immersed, or if the relay is removedfrom its oil bath after the leak occurs, the oil within the containerwill drain out and the operation of the relay will be considerablyaffected by the air which enters the container. When the relay containeris immersed in oil after the oil originally sealed therein has escapedit willpbe found that ratus to be protected is located in a hazardous-yUniform operation vof the the air whichl is trapped within the containerwill substantially prevent the container from refilling with oil, thatis, a diving-bell eiect exists. 'I'he construction of a tightly sealedcontainer may also involve considerable expense.

Much is yet to be desired, therefore, in a ther- 5 mal relay suitablefor oil immersed operation in which provision is made forensuring thatthe Working parts of the/relay are subjected at all times to the properimmersing medium, the relay being designed for low watt input whensubjected 10 to that medium. Accordingly, it is a further object of myinvention to provide a simple and inexpensive thermal relay theoperation of which is reliable and uniform when immersed in oil.

In carrying out my invention in one form, I l5v provide a container forthe thermal operating parts of the relay comprising walls of thermalinsulating material, at least one of the Walls having an aperturetherein for the admission of oil when the device is immersed in a bodyof oil. Such a 20 device is described and broadly claimed in a copendlngapplication of Charles H. Chapman, Serial No. 43,741 led October 5,1935, entitled Temperature overload relay, which application i isassigned to the same assignee as the present invention. The presentinvention is an improvement of the invention disclosed in the above ap'--plication, which invention was madeby the said Charles H. Chapman priorto my invention and I, therefore, do not herein claim anything shown 30or described in that application, which is to be regarded as prior art.When the relay is immersed in a body of oil, sufllcient oil ilowsthrough the aperture in the container wall substantially toA fill thecontainer, the walls being arranged in 3`5 a non-airtight manner so asto prevent the entrapping of air therewithin. The restricted characterof the aperture is such as substantially to isolate the thermaloperating parts of the relay and the oil within the container from themain 40 body of oil so as to minimizethe transfer of heat therebetween.

More specifically I provide a thermal insulat-` ing container withinwhich is supported a. `core having an axially extending slot therein,a'heat- 45 ing winding surrounding the core and a bimetallic elementdisposed in the slot with an end thereof adjacent a movable member whichextends through an aperture in the container wall to control theexternal contactsg- In order 4elec 50 trically to insulate the workingparts of the relay from the circuit to be protected, the core is formedof magnetizable material and the heat-A ing winding comprises a closedcircuited second.- `iuy inductively. related to a primary Winding,

Same.

Referring now to the drawing,thepreferred embodiment of my inventionshown comprises a base I0 of thermal insulating material having a pairof intersecting recesses II and I2 respectively formed therein. Disposedin the recess II is a core member I3 secured to the base Ill as by thescrew I4 and provided with an axially extending slot I5 in which abimetallic element I6 is disposed, with one end thereof secured to aheating member comprising a cylindrical conductor I1 closely surroundingthe portion of the core I3 which extends outwardly from the base I0. Theoutermost end of the core I3 is threaded as shown at I8 and is engagedby a cap I9 of thermal insulating material one face of which is providedwith a groove 20 to form shoulders for positioning a cylindrical member2l of thermal insulating material which surrounds the cylindricalconductor I1, with its opposite end abutting against a face of the baseI0 which is provided with a positioning shoulder 22.

It will be apparent that the cap I9, the cylinder '2l and the base I0comprise the walls of a nonairtight 4container for the thermal workingparts of the relay, no sealing means being provided between the walls,the intersecting recesses II and I2 forming an aperture in one of thewalls. It is highly important that the walls of the container bearranged in a non-airtight manner so as to allow the escape of airtherefrom when the relay is `immersed in oil, and in some cases it maybe desirable to provide a second aperture inthe container.

the bimetallic element I6 and the core I3 which are arranged to occupy aminimum of space, with a substantial portion of the bimetallic elementenclosed on three sides by the core which is formed of heat storagematerial and on the fourth side by the heating member I1 to provide ahigh degree of heat transfer to the bimetallic element. The free end ofthe bimetallic element I6 is adjacent the intersection of the recessesII and I2 and engages one end of a movable member comprising a floatingplunger 23 of insulating material arranged in the recess I2, sufficientclearance being provided between the plunger and the walls of the recessto permit oil to iiow ltherethrough into the container. -I'n Fig. 1 a'portion ofv the plunger. 23 is broken away more clearly to show thearrangement of the circuit controlling contacts.

Supported externally of the container on a face of the base I0adjacentthe recess II, I provide a pair of movable contacts 24 and 25,respectively carried by a pair, of spring arms 26 and 21 which aresupported respectively on the terminal-members 28 and 29 fastened to thebase I0 as by the screws 30. The spring arms 26 and 21 are arrangednormally to bias the contacts 24 and 25 into engagement with each other,the spring arm 26 which exerts a relatively greater biasing The thermalworking parts of-the relay comprise the heating memberv II,I

aosiso force than the spring arm 21 being provided with an adjustablestop 3l for adjusting the normal position of the contacts relative tothe movable member 23 which is disposed as shown to engage thel springarm 21 and move the contact 25 away from the contact 24 when thebimetallic element I6 ilexes to operate the movable member. It will beapparent that by adjusting the stop member 3|, the initial position ofthe contacts 24 and 25 may be adjusted to predetermine the amount offlexure of the bimetallic element I6 which will be necessary todisengage the contacts 24 and 25. Supported on the terminal member 29and extending along the spring arm 21, I provide a guard piece 32 whichserves as a stop for the spring arm 21 and also protects the contactarrangement from injury due to accidental blows.

Although any-'suitable means may be employed for producing a flow ofcurrent through the heating member I1 to heat the thermal Working partsof the relay in accordance with the heating conditions in the circuit tobe protected, I prefer, in order electrically to insulate the thermalworking parts of the relay from the circuit to be protected, to form thecore member I3 of magnetizable material and to arrange the heatingmember I1 as a closed circuited secondary winding which is inductivelyrelated to a primary winding 33 supported on an insulating spool 34surrounding the insulating cylinder 2l. Surrounding the primary winding33, I provide an insulating cylinder 35 arranged concentrically with theinsulating cylinder 2| and having its respective opposite ends abuttingthe base I0 and the end cap, I9 which are respectively provided withsuitable positioning shoulders 36 and 31. The cylinder 35, which maybeomitted Without greatly aecting the operation of the relay, is providedwith a pair of apertures 38 and 39 through which suitable connectingleads may extend from the primary Winding 33 to the circuit to beprotected. Itwill be apparent that the apertures 38 and 39 also permitthe escape of air from the cylinders 2D and 35, and the dow of oilthereinto.

It will be observed that this embodiment of my invention is in eilect, acombination of a current transformer and a thermal relay. Accordingly,the relay is very flexible in its application and may bc applied to theprotectionof apparatus designed to operate at any value of voltagewithin practi- 'cal limits simply by employing a properly wound primarywinding.

When the relayV is immersed in a body of oil9 sumcient oil seeps intothe container substantially to fill the slot I5 in the core member I3and when the primary winding 35 is connected in circuit with theapparatus to be protected, a. magnetic flux will be produced in themagnetizable core 'I3 which will induce a current in the closedcircuited secondary winding comprising the heating member I1, theheating effect of which will be proportional to the heating effect ofthe current flowing in the apparatus to be protected. The heat generatedin the heating member I'I is conducted therefrom to the bimetallicelement, to the core member I3 and to the oil contained in the slot I5,and upon the occurrence of an overload of sunlcient magnitude andduration to endanger the apparatus to be protected, there will besuiiicient heat transferred to the bimetalllc element I6 to cause thebimetallic element to flex. When the free end of the bimetallic elementI8 moves upwardly as viewed in the drawing, the plunger 23 is movedupwardly in the recess I2 to engage the spring'arm 21 and open thecontacts 24 and 25.

It will be apparent now that I have provided an improved thermal relayin which the control contacts and the thermal working parts of the relayare electrically insulated from each other and from the circuit to beprotected, all of the elements being immersed in oil, and in which theworking parts of the relay are substantially thermally isolated from themain body of immersing oil.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto 'sincemany modifications may bemade and I, therefore, contempla-te by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:-

1. A thermal relay comprising a core having a slot extending axiallythereof, a heating member adapted to be heated'by current ow thereincomprising a conductor body closely surrounding said core and athermo-responsive device disposed in said slot to be inuenced by saidheating member. l

2. A thermal relay comprising a core having an axially extending slottherein, a heating winding closely surrounding said core, a bimetallicelement disposed in said slot to be inuenced by said heating winding,and relatively movable contacts controlled by said bimetallic element.

3. A thermal relay comprising a magnetizable core having an axiallyextending slot therein, a closed circuited winding surrounding saidcore,

mea-ns for producing a magnetic flux in said core to induce a heatingcurrent in said closed circuited winding, and a thermo-responsive devicedisposed in said slot to be thermally iniluenced by said closedcircuited Winding.

i. A thermal relay comprising a magnetizable core having` an axiallyextending slot therein, n single-turn closed circuited windingcomprising a conductor body surrounding said core, means for producing amagnetic iiux in said core to induce a heating current in said conductorbody, a bimetallic element disposed in said slot to be thermallyinfluenced by said conductor body, and relatively movable contactscontrolled by said bimetallic element. Y

5. A thermal relay comprising a primary winding, a magnetiaable coredisposed within and spaced from said winding, said core having a slotextending axially thereof, a closed circulted heating windingsurrounding said core in inductive relation with said primary Windingand a thermorwponsive device disposed. in solo: slot to be thermollylnuenceol by said closed clrcuited Winsl-v 6. A thermal relay comprisinge. primary Windable contacts controlled by said bimetallic ele-- ment.

t. A. thermal relay comprising walls oi thermal insulating materialarranged to form a container, one of said walls having an aperturetherein, relatively movable contacts supported externally of saidcontainer, means including a movable member extending through saidaperture for controlling said contacts, a movable. thermo-responsiveelement within said container having a portion ,engaging said movablemember, and means within said container for heating saidthermo-responsive element tol operate said movable member.

8. A thermal relay comprising walls of thermal insulating materialarranged to form a container, one of said walls having Aan aperturetherein, relatively movable contacts supported externally of saidcontainer, means including a e movable member extending through saidaperture for controlling said contacts, a heating member adapted to beheated by current ow therein comprising a cylindrical conductor withinsaid container and a bimetallic element having a portion extendingwithin said cylindrical conductor to be thermally inuenced thereby andanother portion arranged to operate said movable member.

9. A thermal relay comprising walls of thermal insulating materialarranged to form a container,

one of Said walls having an aperture therein, relatively movablecontacts supported externally of said container, means including amovable member extending through said aperture for controlling saidcontacts, a bimetallic element within said container arranged to operatesaid ymovable member, a closed circuited heating winding within saidcontainer thermally associated with said bimetalllc element, and meansdisposed externally oi said container for inducing aheating current insaid closed circuited winding to influence i said bimetallic element.

i0. A thermal relay comprising walls of thermal insulating materialarranged to form a container, one oi said `tvalls having an aperturetherein' a core within said container having a slot extending axiallythereof, a heating winding surrounding said core, a movablethermo-responsive element disposed in said slot to be influenced by saidheating,` winding, a movable member extending through said aperturearranged to be operated by said thermo-responsive element and relativelymovable contacts supported externally ot; said container controlled bysaid movable member.

lli. A thermal relay comprising walls of thermal insulating materialarranged to form a connosed in said slot to be thermally inuenced by--said winding, e, movable lmember extending through said aperturearranged to be operated by said bimetallic element and relativelymovable contacts supported externally of said container controlled bysaid movable member.

l2. A thermal relay comprising walls oi thermal insulating materialarranged toform a container, one of said `Walls having an aperturetherein, a magnetizalole core within said container having a slotextending axially thereof, a single-turn secondary winding comprising acons doctor body closely surrounding said core, means including aprimary winding surrounding said container for producing a iiux in saidcore to induce a heating current in said conductor body,

a bimetallic element disposed in said slot to loe thermally influencedby said conductor body, va movable member extending through saidaperture arranged to be operated by said bimetallic element andrelatively movable contacts supported externally of said containercontrolled by said movable member.

13. A thermal relay comprising walls of thermal insulating materialarranged to form a container, one of said Walls having an aperturetherein, a magnetizable core Within said container having a slotextending axially thereof, a heating member comprising a cylindricalconductor surrounding said core, means'including a primary windingsurrounding said container for producing a ux in said core to induce aheating current in said cylindrical conductor, a bimetallic elementdisposed in said slot having one end secured to said cylindricalconductor, a movable member extending through said aperture arranged tobe operated by said bimetallic element and relatively movable contactssupported externally of said container controlled by said movablemember.

' 14. A thermal relay comprising a base of insulatingv material having apair of intersecting recesses therein, Walls of thermal insulatingmaterial cooperating with said base to form a container enclosing one ofsaid recesses, a bimetallic element supported in said container with amovable portion thereof extending into said one recess, a movable memberdisposed in said other recess to be operated by said bimetallic element,

relatively movable contacts supported on said base adjacent said otherrecess to be controlled by said movable member, and means for heatingsaid bimetallic element. f

15. A thermal relay comprising a base of thermal insulating materialhaving a pair of intersecting recesses therein, a core supported in oneof said recesses and extending outwardly from said base, said corehaving a slot extending axially thereof, a movable thermo-responsiveelement arranged in said slot with a portion thereof adjacent theintersection or' said recesses, a movable member disposed in said otherrecess to be operated by said thermo-responsive element, relativelymovable contacts supported on said base to be controlled by said movablemember, Walls of thermal insulating material cooperating with said baseto enclose said core and said therino-responsive element, and meansWithin said enclosing walls for heating said thermo-responsive elementto operate said movable member.

- 16. A thermal relay comprising a base or" insulatingl material havinga pair of intersecting recesses therein, a magnetizable core supportedin one of said recesses and extending outwardly from said base, saidcore having a slot extending axially thereof, a, bimetallic elementdisposed in said slot with a movable portion thereof vadjacent theintersection of said recesses, a movable inember disposed in said otherrecess to be operated by said bimetallic element,- relatively movablecontacts supported on said base to be controlled by said movable member,Walls of insulating material cooperating with said base to enclosesaidcoreand said bimetallic element, agclosed circuited windingsurrounding said core'vvithin said enclosing walls, and means disposedexternally of said enclosing Walls for producinga nur: in .saidmagnetizable 'core to induce a heating current in said closed circuitedWinding whereby saidbimetallic element is heated to able member. f

operate said moving end of said accingo Vmovable member disposed in saidother recess to be operated by said bimetallic element, relativelymovable contacts supported on said base to be controlled by said movablemember, Walls of thermal insulating material cooperating vwith said baseto enclose said core and said heating member, and means including aprimary Winding surrounding said enclsing Walls for producing a flux insaid magnetizable core to induce a heating current in said heatingmember whereby said bimetallic element is heated to operate said movablemember. f

i8. A thermal relay comprising a base of thermal insulating materialhaving a pair of interseating recesses therein, a magnetizable coresupported in one of said recesses and extending out- Wardly from saidbase, a pair of spaced concentric cylinders of insulating materialsurrounding v said core and having their adjacent ends abutting saidbase, a cap member of thermal insulating material threadedly supportedon the extendcore abutting the opposite adjacent ends of said spacedcylinders, said cap and l said base being provided with concentricshoulders for positioning said spaced cylinders to form a containerhaving inner and outer spaced Walls, a primary winding disposedybetweensaid spaced walls surrounding said inner Wall, a heating membercomprising a cylindrical conductor disposed Within said inner wall ininductive relation with said primary winding surrounding saidmagnetizable core, a bimetallic element disposed in said slot having oneend directly secured to said heat- `ing member, said bimetallic elementhaving its free end adjacentv the intersection of said recesses, amovable member disposed in said other recess to be operated by saidbimetallic element and relatively movable contacts supported on saidbase to be controlled by said movable member.

19. ln a relay having a movable member, a movable contact biased towardsaid member, a second movable contact engaging said rst contact andbiased in the opposite direction, the biasing force on said secondcontact predominatihg whereby the resultant biasing force urges saidengaging contacts away from said movable member, and means including anadjustable stop member associated with said second contact forpositioning said engaging contacts relative to said movable member, saidmovable member being arranged when operated to move said first contacttacts.

205. A thermal relay comprising a member. movable in accordance with thethermal condition of .arm predominating whereby said engaging con-y'tacts' are biased away from said movable memy ber, and means includingan adjustable stop eni against `the bias thereon to disengage said conaheating current in said closed circuited windgaging said second springarm for positioning said engaging contacts relative to said movablemember, said movable member being arranged to engage said rst spring armto open said contacts upon the occurrence of a thermal conditionpredetermined by the adjustment of said stop.

21. A thermal relay adapted for oil immersed operation comprising wallsof thermal insulating material arranged to form a perforate container,the degree of perforation being such as to permit said containersubstantially to fill with oil when said container is immersed in a bodyof oil, the relatively small body of oil within said container beingthermally insulated from the main body of oil, a thermo-responsivedevice disposed within said container, a closed circuited heatingwinding within said container thermally related to saidthermo-responsive device, and means arranged externally of saidcontainer for inducing ing to iniluence said thermo-responsive device.

22. A thermal relay adapted for oil immersed operation comprising wallsof thermal insulating,

material arranged toform a perforate container, the degree ofperforation being such as to permit said container substantially to llwith oil when said container is immersed in a body of oil, therelatively small body of oil within said container being thermallyinsulated from the main. body of oil, a bimetallic element disposedwithin said container, a closed circuited winding thermally related tosaid bimetallic element within said container, and means including aprimary winding surrounding said container for inducing a heatingcurrent in said closed circuited winding thermally to influence saidbimetallic element.

BENJAMIN W. JONES.

